Art of forming and utilizing electron-beams of noncircular cross section



Sept 2, 1952 E. FLORY 3 3 ART OF FORMING AND UTILIZING ELECTRON-BEAMS OF NONCIRCULAR C 8 SECTION Filed Oct. 1950 INVENT R 3% Leslie EJ 10111 @Zww ATTORNEY Patented Sept. 2, 1952 ART OF-FbRMING AND UTILIZING ELEC- I TRON-BEAMS OF NONCIRCULAR CROSS SECTION Leslie E. Flory, Princeton, 'N. J., assignor to Radio Corporation of America, acorporation of Delaware 7 7 Application October 31, 1950, Serial No. 193,217 I This invention relates to the art of forming and utilizing electron-beams of non-circular cross-section.

The electron-beams used in conventional cathode-ray tubes are circular in cross-section. The present invention is predicated upon an appreciation of the fact that a non-circular beam can be used to advantage in any typefof scanning tube whereinit is'desirable to provide an abrupt change in current when the beam is moved in one direction of scan and. a gradual change in current when the beam is moved in another direction, e. g. at a right angle with respect to the first.

'It would appear that a stream of electrons could be endowed with any desired cross-sew tional contoursimply by passing the stream through a mask-aperture of the desired shape and dimensions. :Such indeed is the'case. However, this more or less obvious way of shaping the beam has several disadvantages; (I) the electrons that strike the masking surface are efiectively lost, hence the electron current available on the far side of the mask may comprise a mere fraction of that available at the source or vertual source of the beam; (11) it is not easy to cut and to align rectangular or other odd-shape apertures 01 the minute dimensions normally used in cathode-ray tubes,. (III) any inaccuracies in the contour of the beam, thus shaped, can not be corrected during the operation of the tube or, in fact, at any time subsequent to the assembly of the tube elements.

Accordingly, the principal object of the present invention is to obviate the foregoing. and other disadvantages of present day beam-shaping methods and to provide an improved method of and apparatus for achieving an electron-beam of a non-circular cross-sectional contour.

Another object of the invention is to provide a novel way of converting a stream of electrons into an electron spot having a length-to-width ratio that may be altered or varied while the beam is on.

Another and important object of the present invention is to provide an improved electronbeam tube of the kind provided with a mosaic target electrode and one wherein changes in the output current of the tube shall be achieved without the generation of parasitic currents or transients such as might be occasioned by the presence of insulating material between the elemental conductive areas of the mosaic.

Stated generally, the foregoing andother objects are achieved in accordance with the in-v vention by subjecting an electron-beam of con i v 7 Claims. (01. 313-422) Y ventional circular cross-section, contour to the action of an electron-lens of aspecial construc tion calculated to endow the beam with a desired degree or amount of cylindrical asymmetry. No odd-shape masking apertures are employed. The lens-elements that dolthe trick may form part of the gun. of the tube and may be electrically insulated; from itsother lens elements]; so that .the degree of cylindricity oriasymmetry} introduced into the beam-shaping lens-field may be varied while the device" isinoperation. When applied to. a cathodeeraytube of the coding variety the advantages of the invention are fully realizedwh'en mosaic target toward which.

the non circular. beam is directed comprises a plurality of conductive" elemental areas which are interconnected in a novel manner, to prevent the generation of transient currents during the movement of the beam from onelarea to another.

'Ihe invention is described in greater detail in connection with the accompanying single sheet Fig. Bis a view in perspective of a part ofthe I mosaic target a d; v

Fig. 4' is a. similar view of another form of a mosaic target electrode which may usefully be employed in practicing the invention.

In Fig; 1 of the drawing'the invention is shown as applied to a cathode-ray tube of the coding variety described by Sziklai and Jensen in copending application Serial No. 119,135, filed October 1, 1949. Such tubes maybe used, "by Way of example, in a color television system' to render the system compatible with black and white transmission. I In such a system, the level of the transmitted signal represents the total' intensities of the component colors of the scanned image. As described in detail in said earlier. filed disclosure, color information is transmitted by coding the transmitted wave within, predetermined levels. As'above indicated, the

electrode of the tube of Fig 1 cathode-ray tube here illustrated comprises an there is an electrostatic shield within said space. This shield here takes the form of a metal funnel disposed about the central axis of the tube with its spout 5a extending a limited distance into the neck I. As in the tube of the Sziklai et al disclosure, the main chamber 5 3 contain coding electrode 1." This target. electrode corh'p'rises an "insulating foundation plate 1' having a mosaic target surface made up of from say, twenty to one hundred, spacedapart conductive areas la, Tb; etc. Each conductive element of the mosaic "will be under-'5 stood to be provided with its own external connection, exemplified by the leads 9. As will hereinafter more fully appeafig; mosaic surface of electrode 1 comprises the target fer an electron-beam ll of non-circular cross-section (see Fig. 3).

The non-circular electron beam It is derived from an electron stream or cloud Ila hf ihdifferent contour and dimensions that emanates The ficii'ciilar team "ll'b 'is centered, into a beam suhsfiafiuany reetejnsmar erese-steam by introducing a controlled amount of cylindri i lity'ihtb thebt eiwlse "symmetrical ereetr'ostatic field "cent ally pre ent between the last two diaphragriisfl and '75 erfiniefgun. 'T-he added 'cylihdricity, er' ersymmetrie "fieldfis provided by "a pair of lens 'ele'i'rihtsin the form of short wire-lik e -or rod-like risers 3i and 32 dispbsed in pera11e ffeietiqnshi on opposite sides of the 'aiirture 2 521 {in the las'tfliabhragm 2 5. It may here be noted "that the beam does-hot acquire. itsult'iiiiate creetarig'ular" (or elliptical) cross-sectional contour "until "it reaches a Team aerate-m te the target I Aiii aesi'fea, ratio (e. 7g. t"o "l or more) of leirigth fo vfiidthof'tlie teemspot can be'achieved either eleotricfallyfasflin .Fig. 1, by c6ri'trollin'g the potential 1' app' id to 'the'i'comm on lead'33fof the lr isler'neiits 3I, 3 2 (Sr mechanically, -as=in Fig. 2, eye. proper selection of 'the elevation of said el'ef nients' with respect to theplaneof the inner sulrfalde of the diaphragm 25. J 7

the lngth-to width mm of the-beam spot is to be variedelectrically, the lens elements-3| and if? n us't be insulated from the metal diaphragm 25. As shown in -Fig.-l fshe necessary insulation and support is 'pr ovided by insulating inserts 34. These insulators 34 'are -aflixed to the =inner surface of the diaphragm intermediate th diaphragm and said lens elements i -he insulating ihsefts n and -lad ts "my 4 omitted in tubes wherein the length-to-width ratio of the beam spot is fixed. In this case, referring to Fig. 2, if the elevation and spacing of the risers 3i and 32' is made substantially equal to the diameter of the circular aperture a in the diaphragm-Q5 meaen emm-weum ratio of the spot tat its point ofimp'ingerhent upon the target) is about 50 to 1.

It has been found that the beam l l in moving over the target will generate transient parasitic 'curients i'f Ither'e/i's -any insulating material in the path ofthe be'am, between the conductive elementary-areas la, lb'etc. of which the mosaic i's "cbinpris'ed. Thusgfif the mosaic electrode is or thetypeigsj wn' -a Figs. 1 and 3) wherein the separate conductive areas 1a, lb etc. are supported in'sulating foundation 1', the finite-spaces between the conductive pieces expose parts of the foundation material to the beam. Since the secondary-emission ratio of this insulating inaterial is different from that of the conductive areas Ta, lb -e'to., and since ordinarily there is no control over the potential of "the insulator, the secdnda'ry 'emission em reritreleased by the befam'will vary as determined by the instantaneous :positionbf "the beam'with respect to the conductive and non-conductive parts of Tth'e fr'no's'aio. The transient current generatedwheh Ithe fb'eam pa'sses over "the insulatio'n between "the conductive areas has the ap- (not showifl. "This objection to present mosaic coding electrodes (offth'e construction" the present invention, b t e application of a;

miereseoprean thm'mm ssertones) of evap'og rated inet'al '(e. g. aluminum) over "the entire target surface 'er the mosaic. This surreeefiun or 'la je"r 35 should 'b'e thick enough to "form a slightly 'eenuueu e path between the individual not thick "as to, interfere with the application '65 rep'er "direct entrant pcstenuais "to "said areas "or eofresponuirig to 'aie'sistanqe of about 10 ohms (between adjacent elni'e'nt'a'l areas is 're'commende'd. 'The pac between "the elements j'm,

is not espeeiein cemente with the relative arrangement ef'the eiementtei conductive "area's 1a, 1b, em, 'tha't .iriake "up the target surface of the mosaic-electrode. In this conncti'oh, at-

te'ntionf'is called'to :the fact that'the arrangemerit (if "the conductive "areas along araua diagonals of theitarget, as sho'wn'in Fig'sJl and 3; is claimed by Sziklai and Jensen in- 'coe'pendi'rl'g application'serial No. 119,135 filed "Octoberfil, 1949. v

'The horizontaland vertical patternof theconi ductive elements of the mosaic, shown in'Fi'g."4,

is similar to the pattern employed inthe targt electrode-sh0wn inthe sole application-of: Szikla'i, Y

Serial N 1133318 filed eugustti,1949. LlIn this case, inorder to provide-direct transitionofthe beam fronr-one conductive element to thGqHGK-t without the generation-of transient currents th'e conductors; which 'arefhere designated 31a, 3'71), etc. "are disposeds'hirigle fashioh, -i.' e-., with the J marginal edges of the conductors of one row overlapping the adjacent marginal edges of the conductors of the next row, but electrically isolated therefrom by insulating strips 39 disposed between said marginal edges out of the path of the beam.

The orientation of the long and short crosssectional axes of the rectangular beam spot Il may be fixed as determined by the particular pattern of conductive areas of the mosaic. Thus, where the mosaic has a diagonal pattern as in Figs. 1 and 3, the auxiliary lens elements 3| and 32 should be tilted with respect to the horizontal, as shown in Fig. 1, so that the long axis of the spot falls parallel to the diagonally inclined edges of the conductive areas 1a, lb etc. When the conductive areas of the mosaic target electrode are arranged in parallel horizontal and vertical rows, as in Fig. 4, the auxiliary lens elements 3| and 32 should preferably be disposed with their long edges parallel to either the horizontal or the vertical edges of the conductive areas.

It will now be apparent that the present invention provides a novel way of forming and utilizing an electron-beam of non-circular contour, and one which finds especially useful application in the construction and operation of electron beam tubes of the type employing target electrodes of the mosaic" variety.

What is claimed is:

1. An electron-discharge device comprising a source of electrons, an electron-lens including a plurality of metal diaphragms containing aligned apertures of duplicate shape for deriving from said source a beam of electrons of a cross-sectional shape corresponding to the shape of said apertures, and electrode means supported upon one of said diaphragms adjacent to the aperture thereof for altering said cross-sectional shape of said beam.

2. The invention as set forth in claim 1 and wherein said electrode means is electrically insulated from the metal diaphragm upon which it is supported.

3. The invention as set forth in claim 1 and wherein said electrode means comprises a pair of rod-like metal elements disposed in parallel relationship on opposite sides of said aperture.

4. The invention as set forth in claim 3 and wherein the elevation of said rod-like elements with respect to said diaphragm and the spacing of said elements with respect to each other are each substantially equal to the diameter of said aperture.

5. A cathode-ray tube comprising, an evacuated envelope containing a source of electrons, a mosaic target electrode mounted in the path of electrons from said source, said mosaic electrode having a target surface constituted, at least in part, of a plurality of symmetrically disposed rectangular elemental conductive-areas, a plurality of electron-lens elements disposed in the space between said source and said target for deriving an electron-beam of circular cross-section from said source, an auxiliary electrostatic lens system. disposed to the path of said circular electronbeam for converting said beam into an electronbeam having substantially straight sides parallel to the edges of said rectangular elemental areas, and beam deflecting means for moving said straight-sided beam from one elemental to any other elemental area on said target surface.

6. The invention as set forth in claim 5 wherein said rectangular elementalareas extend along lines parallel to a diagonal of said target surface.

7. A cathode-ray tube comprising an evacuated envelope containing a source of electrons, an

electron-lens including a plurality of spaced- REFERENCES CITED The following references are of record in the file of this patent:

Y UNITED STATES PATENTS Number Name Date 2,080,449 Van Ardenne May 18, 1937 2,212,640 Hogan Aug. 27, 1940 2,252,565 Haeff Aug. 12, 1941 2,302,786 McGee et a1 Nov. 24, 1942 

